Current RFID (Radio Frequency Identification) systems are able to replace barcode systems in many applications. RFID tagging of clothes and other items such as groceries is seeing increased interest in the respective industries. RFID tagging of goods allows the goods to be tracked throughout the supply chain. At the end of the supply chain is the point of sales (POS) application. Typically, a barcode based product scanner is used at the POS to identify the sold products. Based on the information from the POS terminal, all data throughout the supply chain is updated (e.g. inventory) as well as the generation of a customer's bill and deactivation of any security system after customer payment is received.
Barcode POS systems typically have a very low detection range which means that a barcode tag is only readable when positioned such that the barcode tag faces the light beam of the scanner. This typically requires the tagged object to be repositioned until the proper alignment is achieved with the scanner or the scanner needs to be repositioned with respect to the barcode (e.g. handheld scanner) until the proper alignment is achieved as shown in FIGS. 1a-c. FIGS. 1a-b show product 115 with barcode 120 in orientations which do not permit scanner 110 to scan barcode 120. FIG. 1c shows product 115 with barcode 120 oriented such that scanner 110 can scan barcode 120.
Using an RFID system for tagging enables a more efficient way to scan products passing a POS because an RFID tag attached to a product need not be aligned with the antenna. FIGS. 2a-c show some of the alignments permissible in an RFID system with product 215, RFID reader antenna 210 and RFID tag 220. RFID tag 220 may be read using randomly chosen alignments between reader antenna 210 and product 215. Typically RFID systems provide a detection range which results in a larger volume than a barcode system.
Prior art UHF-RFID systems typically have a problem with false positive reads, such as shown in FIG. 3. The electromagnetic radiation pattern of RFID antenna 310 of the reader (not shown) leads to the detection of products 315 with RFID tags 320, 321, 322 and 323 arranged near RFID antenna 310 at POS 300 when only RFID tag 320 on RFID antenna 310 is to be detected. Hence, products 315 from different customers at POS 300 could be read at the same time.